The rules are clear and straightforward (assuming you are in EASA-land),
finding the one for you, however, can be a right challenge.
Google: 'FCL.740'
Bit of jargon helps: right now you are looking to RENEW your expired rating.
Sort things out before expiry - always less painful - and it is called REVALIDATION.
Cutting to the chase, here is the actual requirement:
FCL.740 Validity and renewal of class and type ratings
...
(b) Renewal. If a class or type rating has expired, the applicant shall take the following steps:
(1) pass a proficiency check in accordance with Appendix 9 to this Annex;
(2) prior to the proficiency check referred to in point (1), take refresher training at an ATO, where necessary to reach the level of proficiency to safely operate the relevant class or type of aircraft. However, the applicant may take the training:
(i) at a DTO or at an ATO, where the expired rating was a non-high-performance single-engine piston class rating, .....
(ii) at a DTO, at an ATO or with an instructor, where the rating expired for no more than three years and the rating was a non-high-performance single-engine piston class rating or a TMG class rating.
Enjoy